Since it comes up a lot: the defense bonus is basically extra power, just tacked on in a different way. So 90 power + 20 defense = 110 power. I've been trying (though not doing particularly well) to standardize the power of many of the items of the month at one baseline, and use this to denote an item that's extra strong.

Also had a couple of reports that the airstrike ability disappears from the items list sometimes, and I'll look into that. My guess is it's not carrying over either when someone goes up a level, or when someone exchanges other equipment, so I'll check there tonight.